Purpose. Previous studies using conventional electron microscopy have shown that to generate a significant fraction of outflow resistance, the juxtacanalicular connective tissue (JCT) must be filled with an extracellular matrix gel (Ethier et al., IOVS 27: 1741). The purpose of these studies was to use the recently developed ultrastructural method of quick-freeze/deep-etch to determine whether the "open-spaces" of the JCT were gel-filled and to then calculate the specific hydraulic conductivity K of this region. Methods. Normal human trabecular meshworks were examined using quickfreeze/deep-etch (QFDE). K for the JCT was calculated using a hydrodynamic analysis of morphometric data obtained from electronmicrographs. An identical analysis of bovine corneal stroma was undertaken to calculate a value for K of this tissue and compare it with published values as a means of method validation. Results. In cornea, collagen fibers, with their characteristic banding pattern, and interconnecting filaments were distinguished. The average hydraulic diameter of the "open-spaces" found in corneal stroma was approximately 20 nm. Calculated values of stromal K averaged approximately 1×10-14 cm3, in good agreement with published values obtained from direct measurement. In trabecular meshwork, trabecular beams and the JCT region were identified with good visualization of collagen, elastic fibers and associated matrix. Open, gel-free spaces, much larger than in cornea, but smaller than measured in the JCT by conventional EM, were found with hydraulic diameters as large as 200 nm. Despite this, preliminary hydrodynamic analyses indicated that the number these spaces per unit volume was sufficiently low that the JCT can account for a significant fraction of aqueous outflow resistance. Conclusion. Using QFDE it appears that the JCT has open-spaces for fluid flow. Despite this, the low number of these spaces per unit volume indicates that the JCT may nonetheless generate a significant fraction of aqueous outflow resistance.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience